Desktop app: Add 'Clear context and accept plan' option when accepting a plan

Feature request

In the CLI, when Claude proposes a plan, the first option presented is "Clear context and accept plan", which clears the context window before executing the plan. This option is not available in the desktop app.

Why this matters

It's always ideal for the agent to start plan execution with a clean context window, with only the plan itself loaded. This ensures the agent has maximum context capacity available for the actual work, rather than being weighed down by the conversation history that led to the plan.

Expected behavior

When Claude proposes a plan in the desktop app, the user should be offered the same options as in the CLI, including "Clear context and accept plan" as the primary option.

Current behavior

The desktop app does not offer the "Clear context and accept plan" option — only the standard accept.